Archaeologists in Nottingham say they have uncovered the true site of one of the country's most infamous caves.

Mortimer's Hole is reputed to be the route by which Edward III's troops entered the city's castle to capture Roger de Mortimer, in 1313.

The young Edward is said to have suspected Mortimer of been involved in the murder of his father, Edward II.

The official entrance of Mortimer's Hole is next to Brewhouse Yard but archaeologists

Now believe the real tunnel originates in a garden in the Park Estate.

The discovery was made during the Nottingham Caves Survey, a two-year project in which a laser scanner is being used to produce a three-dimensional record of Nottingham's sandstone caves.

University of Nottingham archaeologist Dr David Walker said: "It's almost certainly the real Mortimer's Hole."

"Early documents talk of a secret passage which the modern one certainly wasn't because it was used for carting stuff up from the River Leen to the castle," he said. "The documents all fit with this tiny sliver of a blocked cave which runs into a man's garden."

Roger de Mortimer was sent to the Tower and then hanged on 29 November 1330.

The archaeologist believes the real Mortimer's Hole is a tunnel currently known as the North-Western Passage.

From the house on Castle Grove in the Park Estate, the passage stretches for 30-40 metres and is partly filled with rubble.

Dr Walker said, once you get past the debris, the full height of the tunnel is exposed and there are rock cut steps at the bottom and an arch at the top.

Filled with rubble

The passage would have emerged in the former Middle Bailey, now the Castle Green, but it is now blocked.

Commenting on the new discovery Dave Green, the man in charge of heritage sites for Nottingham City Council said: "History is always controversial and full of differing opinions and ideas.

"We will look forward to presenting this new information alongside the stories we have always told on our cave tours and leave for the public to choose for themselves which is the real Mortimer's Hole."

The Nottingham Caves Survey began in March 2010.

The team from Trent and Peak Archaeology are producing a record of more than 500 sandstone caves around Nottingham.

So far the team have fully surveyed 35 caves.

"It's been quite a lot of work but it's only a dent in the 500 or so in the city," said Dr Walker.

To be able to survey the caves the archaeologists need to manoeuvre their equipment through the passages.

"We think there's probably about 150 in the city that are still accessible, so we've made a reasonable stab at that.

"We've done quite a wide range of caves in that time in terms of age and uses, from domestic caves to pub cellars to sand mines and tunnels under the castle," he said.

The project, costing £250,000, has been funded by the Greater Nottingham Partnership, East Midlands Development Agency, English Heritage, the University of Nottingham and Nottingham City Council.